with_for_update sqlalchemy 1

with_for_update sqlalchemy

SELECT users.id AS users_id FROM users FOR UPDATE OF users NOWAIT

Here is what the above code is Doing:
1. It’s creating a new session.
2. It’s querying the database for the user with the id of 1.
3. It’s updating the user’s name to “Bob”.
4. It’s committing the session.

The problem is that the above code is not thread-safe. If two threads were to run the above code at the same time, they would both query the database for the user with the id of 1, and then they would both update the user’s name to “Bob”.

To fix this, we need to lock the user’s row in the database. We can do this by using the FOR UPDATE clause in our query.

The above code will now lock the user’s row in the database, and it will not allow any other threads to lock the row until the session is committed.

If another thread tries to lock the row, it will raise an exception.

Similar Posts